In general, an optical fiber has a protective coating layer for protecting a glass fiber, and also has a thin colored layer (hereinafter, referred to as “ink layer”) for distinguishing, as the outermost layer (see, for example, Patent Literature 1). An optical fiber coated with a primary resin layer and the secondary resin layer is wound up once, and thereafter the optical fiber is unwound and the ink layer is formed on the outer periphery of a secondary resin layer. That is, the optical fiber usually has a coating having a three-layered structure of the primary resin layer, the secondary resin layer and the ink layer.
On the other hand, production of an optical fiber by coloring a protective coating layer without any ink layer provided (see, for example, Patent Literature 2) is investigated.